HGI/CASA scientists at USENIX Security and SOUPS with 21 papers

The prestigious conferences will be held in August in Anaheim, California, USA.

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In a few days the renowned "Usenix Security Symposium" (09.-11.8.2023) and the "SOUPS - Symposium on Usable Privacy and Security" (06.-08.8.2023) will take place in Anaheim, California (USA). As in previous years, numerous scientists from Bochum ITS will present their papers at these conferences. Ten papers, some of which are the result of interdisciplinary work, have been accepted for USENIX and four for SOUPS.

An overview of the research papers can be found below.

SOUPS is held annually in conjunction with the Usenix Security Symposium and aims to "bring together an interdisciplinary group of researchers* and practitioners in the areas of human-computer interaction, security, and privacy". The highly regarded Usenix Security Symposium focuses on the security and privacy of computer systems and networks and is aimed at researchers, practitioners, system administrators, and system programmers.


Overview of the papers presented at the Usenix Security Symposium

1. Checking Passwords on Leaky Computers: A Side Channel Analysis of Chrome's Password Leak Detect Protocol. Andrew Kwong, UNC Chapel Hill; Walter Wang, University of Michigan; Jason Kim, Georgia Tech; Jonathan Berger, Bar Ilan University; Daniel Genkin, Georgia Tech; Eyal Ronen, Tel Aviv University; Hovav Shacham, UT Austin; Riad Wahby, CMU; Yuval Yarom, Ruhr University Bochum

Abstract: The scale and frequency of password database compromises has led to widespread and persistent credential stuffing attacks, in which attackers attempt to use credentials leaked from one service to compromise accounts with other services. In response, browser vendors have integrated password leakage detection tools, which automatically check the user's credentials against a list of compromised accounts upon each login, warning the user to change their password if a match is found. In particular, Google Chrome uses a centralized leakage detection service designed by Thomas et al. (USENIX Security '19) that aims to both preserve the user's privacy and hide the server's list of compromised credentials.

In this paper, we show that Chrome's implementation of this protocol is vulnerable to several microarchitectural side-channel attacks that violate its security properties. Specifically, we demonstrate attacks against Chrome's use of the memory-hard hash function scrypt, its hash-to-elliptic curve function, and its modular inversion algorithm. While prior work discussed the theoretical possibility of side-channel attacks on scrypt, we develop new techniques that enable this attack in practice, allowing an attacker to recover the user's password with a single guess when using a dictionary attack. For modular inversion, we present a novel cryptanalysis of the Binary Extended Euclidian Algorithm (BEEA) that extracts its inputs given a single, noisy trace, thereby allowing a malicious server to learn information about a client's password.

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2. ClepsydraCache -- Preventing Cache Attacks with Time-Based Evictions. Jan Philipp Thoma, Ruhr University Bochum; Christian Niesler, University of Duisburg-Essen; Dominic Funke, Gregor Leander, Pierre Mayr, and Nils Pohl, Ruhr University Bochum; Lucas Davi, University of Duisburg-Essen; Tim Güneysu, Ruhr University Bochum & DFKI

Abstract: In the recent past, we have witnessed the shift towards attacks on the microarchitectural CPU level. In particular, cache side-channels play a predominant role as they allow an attacker to exfiltrate secret information by exploiting the CPU microarchitecture. These subtle attacks exploit the architectural visibility of conflicting cache addresses. In this paper, we present CLEPSYDRACACHE, which mitigates state-of-the-art cache attacks using a novel combination of cache decay and index randomization. Each cache entry is linked with a Time-To-Live (TTL) value. We propose a new dynamic scheduling mechanism of the TTL which plays a fundamental role in preventing those attacks while maintaining performance. CLEPSYDRACACHE efficiently protects against the latest cache attacks such as PRIME+(PRUNE+)PROBE. We present a full prototype in gem5 and lay out a proof-of-concept hardware design of the TTL mechanism, which demonstrates the feasibility of deploying CLEPSYDRACACHE in real-world systems.

For details and PDF follow this link


3. "Employees Who Don’t Accept the Time Security Takes Are Not Aware Enough": The CISO View of Human-Centred Security. Jonas Hielscher and Uta Menges, Ruhr University Bochum; Simon Parkin, TU Delft; Annette Kluge and M. Angela Sasse, Ruhr University Bochum

Abstract: In larger organisations, the security controls and policies that protect employees are typically managed by a Chief Information Security Officer (CISO). In research, industry, and policy, there are increasing efforts to relate principles of human behaviour interventions and influence to the practice of the CISO, despite these being complex disciplines in their own right. Here we explore how well the concepts of human-centred security (HCS) have survived exposure to the needs of practice: in an action research approach we engaged with n=30 members of a Swiss-based community of CISOs in five workshop sessions over the course of 8 months, dedicated to discussing HCS.

We coded and analysed over 25 hours of notes we took during the discussions. We found that CISOs far and foremost perceive HCS as what is available on the market, namely awareness and phishing simulations. While they regularly shift responsibility either to the management (by demanding more support) or to the employees (by blaming them) we see a lack of power but also silo-thinking that prevents CISOs from considering actual human behaviour and friction that security causes for employees. We conclude that industry best practices and the state-of-the-art in HCS research are not aligned.

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4. Exploring the Unknown DTLS Universe: Analysis of the DTLS Server Ecosystem on the Internet. Nurullah Erinola and Marcel Maehren, Ruhr University Bochum; Robert Merget, Technology Innovation Institute; Juraj Somorovsky, Paderborn University; Jörg Schwenk, Ruhr University Bochum

Abstract: DTLS aims to bring the same security guarantees as TLS to UDP. It is used for latency-sensitive applications such as VPN, VoIP, video conferencing, and online gaming that can suffer from the overhead of a reliable transport protocol like TCP. While researchers and developers invested significant effort in improving the security of TLS, DTLS implementations have not received the same scrutiny despite their importance and similarity. It is thus an open question whether vulnerabilities discovered in TLS have been fixed in DTLS and whether DTLS-specific features open possibilities for new attacks.

To fill this gap, we extended the open-source tool TLS-Scanner with support for DTLS and implemented additional tests for DTLS-exclusive features. We evaluated twelve open-source DTLS server implementations and uncovered eleven security vulnerabilities, including a padding oracle vulnerability in PionDTLS and DoS amplification vulnerabilities in wolfSSL, Scandium, and JSSE. We then proceeded to scan publicly available servers. We discovered and analyzed more than 500,000 DTLS servers across eight ports providing detailed insights into the publicly accessible DTLS server landscape. Beyond cryptographic vulnerabilities and compatibility issues, our analysis showed that 4.4% of the evaluated servers could be used for DoS amplification attacks due to insufficient care when handling anti-DoS cookies.

For details and PDF follow this link


5. Every Signature is Broken: On the Insecurity of Microsoft Office’s OOXML Signatures. Simon Rohlmann, Vladislav Mladenov, Christian Mainka, Daniel Hirschberger, and Jörg Schwenk, Ruhr University Bochum

Abstract: Microsoft Office is one of the most widely used applications for office documents. For documents of prime importance, such as contracts and invoices, the content can be signed to guarantee authenticity and integrity. Since 2019, security researchers have uncovered attacks against the integrity protection in other office standards like PDF and ODF. Since Microsoft Office documents rely on different specifications and processing rules, the existing attacks are not applicable.

We are the first to provide an in-depth analysis of Office Open XML (OOXML) Signatures, the Ecma/ISO standard that all Microsoft Office applications use. Our analysis reveals major discrepancies between the structure of office documents and the way digital signatures are verified. These discrepancies lead to serious security flaws in the specification and in the implementation. As a result, we discovered five new attack classes. Each attack allows attackers to modify the content in signed documents, while the signatures are still displayed as valid.

We tested the attacks against different Microsoft Office versions on Windows and macOS, as well as against OnlyOffice Desktop on Windows, macOS and Linux. All tested Office versions are vulnerable. On macOS, we could reveal a surprising result: although Microsoft Office indicates that the document is protected by a signature, the signature is not validated. The attacks’ impact is alarming: attackers can arbitrarily manipulate the displayed content of a signed document, and victims are unable to detect the tampering. Even worse, we present a universal signature forgery attack that allows the attacker to create an arbitrary document and apply a signature extracted from a different source, such as an ODF document or a SAML token. For the victim, the document is displayed as validly signed by a trusted entity.

We propose countermeasures to prevent such issues in the future. During a coordinated disclosure, Microsoft acknowledged and awarded our research with a bug bounty.

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Read the press release here


6. Fuzztruction: Using Fault Injection-based Fuzzing to Leverage Implicit Domain Knowledge. Nils Bars, Moritz Schloegel, Tobias Scharnowski, and Nico Schiller, Ruhr-Universität Bochum; Thorsten Holz, CISPA Helmholtz Center for Information Security

Abstract: Today's digital communication relies on complex protocols and specifications for exchanging structured messages and data. Communication naturally involves two endpoints: One generating data and one consuming it. Traditional fuzz testing approaches replace one endpoint, the generator, with a fuzzer and rapidly test many mutated inputs on the target program under test. While this fully automated approach works well for loosely structured formats, this does not hold for highly structured formats, especially those that go through complex transformations such as compression or encryption.

In this work, we propose a novel perspective on generating inputs in highly complex formats without relying on heavyweight program analysis techniques, coarse-grained grammar approximation, or a human domain expert. Instead of mutating the inputs for a target program, we inject faults into the data generation program so that this data is almost of the expected format. Such data bypasses the initial parsing stages in the consumer program and exercises deeper program states, where it triggers more interesting program behavior. To realize this concept, we propose a set of compile-time and run-time analyses to mutate the generator in a targeted manner, so that it remains intact and produces semi-valid outputs that satisfy the constraints of the complex format. We have implemented this approach in a prototype called Fuzztruction and show that it outperforms the state-of-the-art fuzzers AFL++, SYMCC, and WEIZZ. Fuzztruction finds significantly more coverage than existing methods, especially on targets that use cryptographic primitives. During our evaluation, Fuzztruction uncovered 151 unique crashes (after automated deduplication). So far, we manually triaged and reported 27 bugs and 4 CVEs were assigned.

For details and PDF follow this link


7. Hoedur: Embedded Firmware Fuzzing using Multi-Stream Inputs. Tobias Scharnowski and Simon Wörner, CISPA Helmholtz Center for Information Security; Felix Buchmann, Ruhr University Bochum; Nils Bars, Moritz Schloegel, and Thorsten Holz, CISPA Helmholtz Center for Information Security

Abstract: Embedded systems with their diverse, interconnected components form the backbone of our digital infrastructure. Despite their importance, analyzing their security in a scalable way has remained elusive and challenging. Recent firmware rehosting work has brought scalable, dynamic analyses to embedded systems, making fuzzing for automated vulnerability assessments feasible. As these works focus on modeling device behavior rather than fuzzing, they integrate with off-the-shelf fuzzers in an ad-hoc manner. They re-interpret traditional flat binary fuzzing input as a sequence of hardware responses. In practice, this presents the fuzzer with an input layout that is fragile, opaque, and hard to mutate effectively.

Our work is based on the insight that while firmware emulation recently matured significantly, the input space is presented to the fuzzer in an ineffective manner. We propose a novel method for a firmware-aware fuzzing integration based on multi-stream inputs. We reorganize the previously flat, sequential, and opaque firmware fuzzing input into multiple strictly typed and cohesive streams. This allows our fuzzer, HOEDUR, to perform type-aware mutations and maintain its progress. It also enables firmware fuzzing to use state-of-the-art mutation techniques. Overall, we find that these techniques significantly increase fuzzing effectiveness. Our evaluation shows that HOEDUR achieves up to 5x the coverage of stateof-the-art firmware fuzzers, finds bugs that other fuzzers do not, and discovers known bugs up to 550x faster. In total, HOEDUR uncovered 23 previously unknown bugs.

For details and PDF follow this link


8. Hot Pixels: Frequency, Power, and Temperature Attacks on GPUs and Arm SoCs. Hritvik Taneja, Jason Kim, and Jie Jeff Xu, Georgia Tech; Stephan van Schaik, University of Michigan; Daniel Genkin, Georgia Tech; Yuval Yarom, Ruhr University Bochum

Abstract: The drive to create thinner, lighter, and more energy efficient devices has resulted in modern SoCs being forced to balance a delicate tradeoff between power consumption, heat dissipation, and execution speed (i.e., frequency). While beneficial, these DVFS mechanisms have also resulted in software-visible hybrid side-channels, which use software to probe analog properties of computing devices. Such hybrid attacks are an emerging threat that can bypass countermeasures for traditional microarchitectural side-channel attacks.

Given the rise in popularity of both Arm SoCs and GPUs, in this paper we investigate the susceptibility of these devices to information leakage via power, temperature and frequency, as measured via internal sensors. We demonstrate that the sensor data observed correlates with both instructions executed and data processed, allowing us to mount software-visible hybrid side-channel attacks on these devices.

To demonstrate the real-world impact of this issue, we present JavaScript-based pixel stealing and history sniffing attacks on Chrome and Safari, with all side channel countermeasures enabled. Finally, we also show website fingerprinting attacks, without any elevated privileges.

For details and PDF follow this link


9. Instructions Unclear: Undefined Behaviour in Cellular Network Specifications. Daniel Klischies, Ruhr University Bochum; Moritz Schloegel and Tobias Scharnowski, CISPA Helmholtz Center for Information Security; Mikhail Bogodukhov, Independent; David Rupprecht, Radix Security; Veelasha Moonsamy, Ruhr University Bochum

Abstract: Cellular networks are a cornerstone of modern communication and indispensable to our daily lives. Their specifications span thousands of pages, written primarily in natural language. The ensuing complexity and lack of explicitness lead to underspecification, where only subsets of possible interactions are properly specified, while other behaviour is left undefined and open to interpretation by developers. In practice, this causes weird, unintended interactions in smartphone modems implementing the specification that, in the worst case, lead to security vulnerabilities.

In this work, we present the first generic approach for systematically discovering undefined behaviour in cellular specifications. Requiring solely a model of the behaviour defined in the specification, our technique extends this model to automatically reason about the presence of undefined behaviour. For each undefined behaviour, it automatically infers concrete examples as proof of existence. This not only allows improving the specification but also enables us to test smartphone modems. This way, we can verify whether an instance of undefined behaviour leads to a security vulnerability within modem firmware. With our approach, we identify 58 cases of undefined behaviour in LTE's Public Warning System, SMS, and Radio Resource Control specifications. Five of these cases resulted in previously unknown vulnerabilities that allow adversaries to read modem memory contents and perform remote Denial of Service attacks (in one case just via a single SMS) against commonly used smartphone modems. So far, two CVEs of high and one CVE of critical severity have been assigned.

For details and PDF follow this link


10. In the Quest to Protect Users from Side-Channel Attacks – A User-Centred Design Space to Mitigate Thermal Attacks on Public Payment Terminals. Karola Marky, Ruhr-University Bochum and University of Glasgow; Shaun Macdonald, University of Glasgow; Yasmeen Abdrabou, Lancaster University; Mohamed Khamis, University of Glasgow

Abstract: Thermal attacks are an emerging threat that enables the reconstruction of user input after interaction with a device by analysing heat traces. There are several ways to protect users from thermal attacks that require different degrees of user involvement. In this paper, we first present a structured literature review to identify 15 protection strategies. Then, we investigate user perceptions of these strategies in an online study (N=306).

Our results show that users intuitively use protection strategies that also work against other side-channel attacks. Further, users are willing to sacrifice convenience for the sake of verifying a strategy's efficacy. Yet, an ideal holistic defence from thermal attacks is one that is readily integrated into user interfaces by manufacturers in a way that the user can verify it. Further, users like resourceless strategies that fit their habits. We use the literature review and study results to identify a user-centred design space for thermal attack protection. We conclude the paper with specific recommendations for users, device manufacturers and interface providers to better protect individuals from thermal attacks.

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11. Isolated and Exhausted: Attacking Operating Systems via Site Isolation in the Browser. Matthias Gierlings, Marcus Brinkmann, and Jörg Schwenk, Ruhr University Bochum

Abstract: Site Isolation is a security architecture for browsers to protect against side-channel and renderer exploits by separating content from different sites at the operating system (OS) process level. By aligning web and OS security boundaries, Site Isolation promises to defend against these attack classes systematically in a streamlined architecture. However, Site Isolation is a large-scale architectural change that also makes OS resources more accessible to web attackers, and thus exposes web users to new risks at the OS level. In this paper, we present the first systematic study of OS resource exhaustion attacks based on Site Isolation, in the web attacker model, in three steps: (1) first-level resources directly accessible with Site Isolation; (2) second-level resources whose direct use is protected by the browser sandbox; (3) an advanced, real-world attack.

For (1) we show how to create a fork bomb, highlighting conceptual gaps in the Site Isolation architecture. For (2) we show how to block all UDP sockets in an OS, using a variety of advanced browser features. For (3), we implement a fully working DNS Cache Poisoning attack based on Site Isolation, building on (2) and bypassing a major security feature of DNS. Our results show that the interplay between modern browser features and older OS features is increasingly problematic and needs further research.

For details and PDF follow this link


12. No more Reviewer #2: Subverting Automatic Paper-Reviewer Assignment using Adversarial Learning. Thorsten Eisenhofer, Ruhr University Bochum; Erwin Quiring, Ruhr University Bochum and International Computer Science Institute (ISCI) Berkeley; Jonas Möller, Technische Universität Berlin; Doreen Riepel, Ruhr University Bochum; Thorsten Holz, CISPA Helmholtz Center for Information Security; Konrad Rieck, Technische Universität Berlin

Abstract: The number of papers submitted to academic conferences is steadily rising in many scientific disciplines. To handle this growth, systems for automatic paper-reviewer assignments are increasingly used during the reviewing process. These systems use statistical topic models to characterize the content of submissions and automate the assignment to reviewers. In this paper, we show that this automation can be manipulated using adversarial learning. We propose an attack that adapts a given paper so that it misleads the assignment and selects its own reviewers.

Our attack is based on a novel optimization strategy that alternates between the feature space and problem space to realize unobtrusive changes to the paper. To evaluate the feasibility of our attack, we simulate the paper-reviewer assignment of an actual security conference (IEEE S&P) with 165 reviewers on the program committee. Our results show that we can successfully select and remove reviewers without access to the assignment system. Moreover, we demonstrate that the manipulated papers remain plausible and are often indistinguishable from benign submissions.

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13. SCARF – A Low-Latency Block Cipher for Secure Cache-Randomization. Federico Canale, Ruhr-University Bochum; Tim Güneysu, Ruhr-University Bochum and DFKI; Gregor Leander and Jan Philipp Thoma, Ruhr-University Bochum; Yosuke Todo, NTT Social Informatics Laboratories; Rei Ueno, Tohoku University

Abstract: Randomized cache architectures have proven to significantly increase the complexity of contention-based cache side channel attacks and therefore present an important building block for side-channel secure microarchitectures. By randomizing the address-to-cache-index mapping, attackers can no longer trivially construct minimal eviction sets which are fundamental for contention-based cache attacks. At the same time, randomized caches maintain the flexibility of traditional caches, making them broadly applicable across various CPU-types. This is a major advantage over cache partitioning approaches.

A large variety of randomized cache architectures has been proposed. However, the actual randomization function received little attention and is often neglected in these proposals. Since the randomization operates directly on the critical path of the cache lookup, the function needs to have extremely low latency. At the same time, attackers must not be able to bypass the randomization which would nullify the security benefit of the randomized mapping. In this paper we propose SCARF (Secure CAche Randomization Function), the first dedicated cache randomization cipher which achieves low latency and is cryptographically secure in the cache attacker model. The design methodology for this dedicated cache cipher enters new territory in the field of block ciphers with a small 10-bit block length and heavy key-dependency in few rounds.

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14. Systematic Assessment of Fuzzers using Mutation Analysis. Philipp Görz, Björn Mathis, and Keno Hassler, CISPA Helmholtz Center for Information Security; Emre Güler, Ruhr-Universität Bochum; Thorsten Holz and Andreas Zeller, CISPA Helmholtz Center for Information Security; Rahul Gopinath, University of Sydney.

Abstract:Fuzzing is an important method to discover vulnerabilities in programs. Despite considerable progress in this area in the past years, measuring and comparing the effectiveness of fuzzers is still an open research question. In software testing, the gold standard for evaluating test quality is mutation analysis, which evaluates a test's ability to detect synthetic bugs: If a set of tests fails to detect such mutations, it is expected to also fail to detect real bugs. Mutation analysis subsumes various coverage measures and provides a large and diverse set of faults that can be arbitrarily hard to trigger and detect, thus preventing the problems of saturation and overfitting. Unfortunately, the cost of traditional mutation analysis is exorbitant for fuzzing, as mutations need independent evaluation.

In this paper, we apply modern mutation analysis techniques that pool multiple mutations and allow us—for the first time—to evaluate and compare fuzzers with mutation analysis. We introduce an evaluation bench for fuzzers and apply it to a number of popular fuzzers and subjects. In a comprehensive evaluation, we show how we can use it to assess fuzzer performance and measure the impact of improved techniques. The required CPU time remains manageable: 4.09 CPU years are needed to analyze a fuzzer on seven subjects and a total of 141,278 mutations. We find that today's fuzzers can detect only a small percentage of mutations, which should be seen as a challenge for future research—notably in improving (1) detecting failures beyond generic crashes and (2) triggering mutations (and thus faults).

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15. The OK Is Not Enough: A Large Scale Study of Consent Dialogs in Smartphone Applications. Simon Koch, TU Braunschweig; Benjamin Altpeter, e.V.; Martin Johns, TU Braunschweig

Abstract: Mobile applications leaking personal information is a well established observation pre and post GDPR. The legal requirements for personal data collection in the context of tracking are specified by GDPR and the common understanding is, that tracking must be based on proper consent. Studies of the consent dialogs on websites revealed severe issues including dark patterns. However, the mobile space is currently underexplored with initial observations pointing towards a similar state of affairs.

To address this research gap we analyze a subset of possible consent dialogs, namely privacy consent dialogs, in 3006 Android and 1773 iOS applications. We show that 22.3% of all apps have any form of dialog with only 11.9% giving the user some form of actionable choice, e.g., at least an accept button. However, this choice is limited as a large proportion of all such dialogs employ some form of dark pattern coercing the user to consent.

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16. “To Do This Properly, You Need More Resources”: The Hidden Costs of Introducing Simulated Phishing Campaigns. Lina Brunken, Annalina Buckmann, Jonas Hielscher, and M. Angela Sasse, Ruhr University Bochum

Abstract: Many organizations use phishing simulation campaigns to raise and measure their employees' security awareness. They can create their own campaigns, or buy phishing-as-a-service from commercial providers; however, the evaluations of the effectiveness in reducing the vulnerability to such attacks have produced mixed results. Recently, researchers have pointed out "hidden costs" - such as reduced productivity and employee trust. What has not been investigated is the cost involved in preparing an organization for a simulated phishing campaign.

We present the first case study of an organization going through the process of selecting and purchasing a phishing simulation. We document and analyze the effort of different stakeholders involved, and present reflection from semi-structured interviews with 6 key actors at the end of the procurement process. Our data analysis shows that procuring such simulations can require significant effort from different stakeholders - in our case, at least 50,000€ in person hours - and many hidden intangible costs. Evaluating if a product or service meets training requirements, is acceptable to employees, and preparing the technical infrastructure and operational processes for running such a product all require significant time and effort. The prevailing perception that phishing simulation campaigns are a quick and low-cost solution to providing security training to employees thus needs to be challenged.

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17. We Really Need to Talk About Session Tickets: A Large-Scale Analysis of Cryptographic Dangers with TLS Session Tickets. Sven Hebrok, Paderborn University; Simon Nachtigall, Paderborn University and achelos GmbH; Marcel Maehren and Nurullah Erinola, Ruhr University Bochum; Robert Merget, Technology Innovation Institute and Ruhr University Bochum; Juraj Somorovsky, Paderborn University; Jörg Schwenk, Ruhr University Bochum

Abstract: Session tickets improve the performance of the TLS protocol. They allow abbreviating the handshake by using secrets from a previous session. To this end, the server encrypts the secrets using a Session Ticket Encryption Key (STEK) only know to the server, which the client stores as a ticket and sends back upon resumption. The standard leaves details such as data formats, encryption algorithms, and key management to the server implementation.

TLS session tickets have been criticized by security experts, for undermining the security guarantees of TLS. An adversary, who can guess or compromise the STEK, can passively record and decrypt TLS sessions and may impersonate the server. Thus, weak implementations of this mechanism may completely undermine TLS security guarantees. We performed the first systematic large-scale analysis of the cryptographic pitfalls of session ticket implementations. (1) We determined the data formats and cryptographic algorithms used by 12 open-source implementations and designed online and offline tests to identify vulnerable implementations. (2) We performed several large-scale scans and collected session tickets for extended offline analyses. We found significant differences in session ticket implementations and critical security issues in the analyzed servers. Vulnerable servers used weak keys or repeating keystreams in the used tickets, allowing for session ticket decryption. Among others, our analysis revealed a widespread implemen tation flaw within the Amazon AWS ecosystem that allowed for passive traffic decryption for at least 1.9% of the Tranco Top 100k servers.

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Papers auf der SOUPS

1. Lacking the Tools and Support to Fix Friction: Results from an Interview Study with Security Managers. Jonas Hielscher, Markus Schöps, Uta Menges, Marco Gutfleisch, Mirko Helbling, and M. Angela Sasse, Ruhr University Bochum

Abstract: Security managers often perceive employees as the key vulnerability in organizations when it comes to security threats, and complain that employees do not follow secure behaviors defined by their security policies and mechanisms. Research has shown, however, that security often interferes with employees primary job function, causing friction and reducing productivity -- so when employees circumvent security measures, it is to protect their own productivity, and that of the organization. In this study, we explore to what extent security managers are aware of the friction their security measures cause, if they are aware of usable security methods and tools they could apply to reduce friction, and if they have tried to apply them.

We conducted 14 semi-structured interviews with experienced security managers (CISOs and security consultants, with an average 20 years experience) to investigate how security friction is dealt with in organizations. The results of the interviews show security managers are aware that security friction is a significant problem that often reduces productivity and increases the organization's vulnerability. They are also able to identify underlying causes, but are unable to tackle them because the organizations prioritize compliance with relevant external standards, which leaves no place for friction considerations. Given these blockers to reducing security friction in organizations, we identify a number of possible ways forward, such as: including embedding usable security in regulations and norms, developing positive key performance indicators (KPIs) for usable security measures, training security managers, and incorporating usability aspects into the daily processes to ensure security frictionless work routines for everyone.

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2. On the Recruitment of Company Developers for Security Studies: Results from a Qualitative Interview Study. Raphael Serafini, Marco Gutfleisch, Stefan Albert Horstmann, and Alena Naiakshina, Ruhr University Bochum

Abstract: To address the issue of participant recruitment for security developer studies, researchers proposed using freelance online platforms or recruiting computer science (CS) students as proxies. However, recent studies showed that company developers performed better than freelancers or CS students in security developer studies. Additionally, studies on factors influencing usable security and privacy in companies make recruiting professionals indispensable. Therefore, we investigated influential factors on the motivation of software developers regularly employed in companies to participate in security studies.

We conducted 30 semi-structured interviews on their perceptions of study factors concerning study design, recruitment methods, and data collection. We found that the study duration, topic, monetary compensation, and trust are influential factors for participation in developer studies. However, participants were concerned about high effort and weak performance in security tasks. Based on our findings, we provide recruitment and study design recommendations for future security research with company developers.

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3. Privacy Mental Models of Electronic Health Records: A German Case Study. Rebecca Panskus, Ruhr-University Bochum; Max Ninow, Leibniz University Hannover; Sascha Fahl, CISPA Helmholtz Center for Information Security; Karola Marky, Ruhr-University Bochum and Leibniz University Hannover

Abstract: Central digitization of health records bears the potential for better patient care, e.g., by having more accurate diagnoses or placing less burden on patients to inform doctors about their medical history. On the flip side, having electronic health records (EHRs) has privacy implications. Hence, the data management infrastructure needs to be designed and used with care. Otherwise, patients might reject the digitization of their records, or the data might be misused. Germany, in particular, is currently introducing centralized EHRs nationwide. We took this effort as a case study and captured privacy mental models of EHRs.

We present and discuss findings of an interview study where we investigated expectations towards EHRs and perceptions of the German infrastructure. Most participants were positive but skeptical, yet expressed a variety of misconceptions, especially regarding data exchange with health insurance providers and read-write access to their EHRs. Based on our results, we make recommendations for digital infrastructure providers, such as developers, system designers, and healthcare providers.

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4. Tangible 2FA – An In-the-Wild Investigation of User-Defined Tangibles for Two-Factor Authentication. Mark Turner, University of Glasgow; Martin Schmitz, Saarland University Saarbrücken; Morgan Masichi Bierey and Mohamed Khamis, University of Glasgow; Karola Marky, University of Glasgow and Ruhr-University Bochum

Abstract: Although two-factor authentication (2FA) mechanisms can be usable, they poorly integrate into users' daily routines, especially during mobile use. Using tangibles for 2FA is a promising alternative that beneficially combines customisable authentication routines and object geometries, personalisable to each user. Yet, it remains unclear how they integrate into daily routines.

In this paper, we first let 226 participants design 2FA tangibles to understand user preferences. Second, we prototyped the most common shapes and performed a one-week long in-the-wild study (N=15) to investigate how 2FA tangibles perform in different environments. We show that most users prefer objects that a) fit in wallets, b) connect to daily items or c) are standalone. Users enjoyed interacting with 2FA tangibles and considered them a viable and more secure alternative. Yet, they voiced concerns on portability. We conclude by an outlook for a real world implementation and distribution of 2FA tangibles addressing user concerns.

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General note: In case of using gender-assigning attributes we include all those who consider themselves in this gender regardless of their own biological sex.